This invention relates to release liners for adhesive backed articles. More particularly, the invention relates to a release liner for an adhesive backed article that has modified surface geometries that enhance adhesion to handling tapes such as pre-mask tapes, pre-space tapes, splicing tapes and the like.
Pressure sensitive adhesive-backed films may be imaged and adhered to a substrate for decorative purposes. For example, large graphics or smaller decals may be placed on vehicles or may be used as signs for identification, promotional or decorative objectives. However, the tacky and aggressive pressure sensitive adhesives used in these applications cause considerable handling and application problems. Ideally, the film is adhered conformably and evenly on the application substrate. Adhesive-backed articles that adhere with the slightest contact can often be particularly difficult to reapply if they inadvertently adhere to the substrate in an undesired position. In addition, even if one section of the adhesive backed article is properly positioned on a substrate, and the film is firmly adhered, air or other fluids may be trapped under the article. The trapped air forms a bubble in the article, and cannot be easily removed without de-bonding or perforating the article.
The adhesive backed graphic articles described in U.S. Pat. No. 5,897,930, WO 98/29516 and U.S. Ser. No. 09/311,101 (3M File No. 54528USA2A) include an adhesive layer with a plurality of replicated recessed interconnecting microchannels that allow egress of fluids trapped under the article during registration with the substrate. A typical article 10 of this type is shown in FIG. 1, and includes a film 12 having opposed surfaces 14 and 16. The surface 14 of the film 12 is imaged to form a graphic 13. A layer of a pressure sensitive adhesive 18 is bonded to the surface 16 of the film 12. The pressure sensitive adhesive 18 includes a surface 20 that can be bonded to a substrate. The pressure sensitive adhesive 18 includes structures 22 that define a network of channels 24. A release liner 26 is releasably attached to the pressure sensitive adhesive 18. The release liner 26 includes protrusions 28 that form the corresponding channels 24 and structures 22 in the pressure sensitive adhesive 18. The release liner 26, shown in a partially removed state, is fully detachable when pulled in the direction of arrow A and is used to protect the pressure sensitive adhesive prior to application of the article 10 on a substrate.
As the adhesive backed graphic articles shown in FIG. 1 are manufactured, a splicing tape may be used in the production process to adhere the protective release liner (See 26 in FIG. 1) from one roll onto the release liner from another roll. Prior to application to a substrate, pre-mask or pre-space tapes may be used to protect the graphics, aid in handling the graphic article, or to transfer cut graphics from the liner into proper registration with the substrate. If the graphics are cut and a portion of the surrounding un-imaged film and adhesive layer are removed, the release liner is exposed, and the pre-mask and pre-space tapes should adhere sufficiently to the release liner to allow transfer of the graphic article into proper registration with the substrate.
If a release liner includes a network of continuous ridges spaced closely together (See 28 in FIG. 1), only a relatively small surface area on the tops of the ridges is available for bonding to a pre-mask, a pre-space, or a splicing tape. The closely spaced ridges also make it more difficult for the tapes to contact and adhere to the relatively flat land areas between the ridges. The pre-mask, pre-space or splicing tapes have specific conformability and adhesion requirements that enable them to perform their protective and transferability functions, and these requirements cannot be easily modified to enhance adhesion to a release liner.
Rather than chemically modify the pre-mask, pre-space or splicing tapes to enhance adhesion to a release liner, the invention seeks to mechanically modify the features on the release liner itself to allow the tapes to more effectively adhere to the liner. The release liners of the invention include structures with geometries that improve the adhesion of tapes to the liner without sacrifice of the application, bonding and visual properties of the final graphic film product.
In a first embodiment, the invention is a release liner having a surface with an arrangement of protruding structures thereon. The structures extend upward from a plane of the surface and have at least one sidewall that makes an angle with respect to the plane of the surface of greater than 0xc2x0 and less than 90xc2x0 selected to enhance adhesion to a handling tape such as a pre-space tape, a pre-mask tape, a splicing tape and the like. Preferably, the structures have at least one sidewall that makes an angle of less than about 50xc2x0 with respect to the plane of the surface.
In a second embodiment, the invention is an adhesive backed article including:
(a) a release liner having a surface with an arrangement of structures thereon, wherein the structures extend upward from a plane of the surface, and wherein the structures have at least one sidewall that makes an angle with respect to the plane of the surface of greater than 0xc2x0 and less than 90xc2x0 selected to enhance adhesion to a handling tape; and
(b) an adhesive layer on the surface of the release liner.
In a third embodiment, the invention is a method of enhancing the adhesion of a tape to a release liner, comprising providing on the release liner an arrangement of structures extending upward from a plane of the surface, wherein the structures have at least one sidewall that makes an angle with respect to the plane of the surface of greater than 0xc2x0 and less than 90xc2x0 selected to enhance adhesion to the tape.
In a fourth embodiment, the invention is a method of transferring an adhesive backed article with a release liner and an adhesive layer on the release liner. The method includes attaching a tape to the release liner, wherein the release liner has an arrangement of structures extending upward from a plane of a surface of the liner. The structures have at least one sidewall that makes an angle with respect to the plane of the surface of greater than 0xc2x0 and less than 90xc2x0 selected to enhance adhesion to the tape.
In a fifth embodiment, the invention is a method of transferring a graphic article including:
(a) providing a graphic article including:
a film with a first surface and a second surface, wherein an image occupies at least a portion of the first surface;
an adhesive layer on the second surface of the film;
a release liner on the adhesive layer, wherein the release liner comprises a surface with an arrangement of structures thereon, wherein the structures extend upward from a plane of the surface, and wherein the structures have at least one sidewall that makes an angle with respect to the plane of the surface of greater than 0xc2x0 and less than 90xc2x0 selected to enhance adhesion to a handling tape;
(b) removing the film and the adhesive layer under portions of the first surface not occupied by the image such that at least a portion of the surface of the release liner is exposed;
(c) attaching a handling tape to the image and the exposed portion of the release liner; and
(d) transferring the article into registration with a substrate.
In an optional additional step, the handling film is removed from the substrate and the graphic article.